The present invention relates in general to a hand guided plane driven by electric motor, and in particular to a plane of the type that includes a housing, a handle on the housing, a rotary shaft arranged within the housing for supporting at least one planing knife, a first guiding plate mounted on the housing and adjoining the path of movement of the planing knife, an adjustable shoe guided in the housing, a second guiding plate formed on the shoe and being substantially flush with the first guiding plate, and an adjustment device mounted on the housing and engaging the shoe.
A plane of this type, driven by an electric motor, is disclosed in the U.S. Pat. No. 3,407,857. This known plane has a housing provided with a yoke-shaped handle, a rotary shaft supporting a planing knife for orbiting in the housing, a first guiding plate connected to the housing and being directed parallel to the rotary shaft, an adjustable shoe guided substantially at right angles to the first guiding plate and being formed with a second guiding plate extending flush with the first guiding plate, and an adjustment device for the shoe. The adjustment device engages the shoe and thus the second guiding plate in such a manner that the latter is vertically adjusted relative to the path of movement of planing knife mounted on the rotary shaft and thus adjusts the depth of cut of the plane. The prior-art adjustment device consists of a hexagonal screw which is directed perpendicularly to the path of movement of the setting shoe and connected to the housing; a lever pivotable about the axis of the hexagonal screw and being formed with an eccentric; and a sliding ring surrounding the eccentric, the ring being displaceable in a slot formed in the adjustment device and extending parallel to the second guiding plate. By tilting the lever the eccentric is rotated and displaces the sliding ring along the slot, thus moving the adjustment device relative to the first guiding plate. The disadvantage of this known adjustment device is the fact that it is composed of many complicated component parts which must engage each other substantially without play. Consequently, the production of such accurate component parts is very expensive.
From the German patent publications (Gebrauchmusters) Nos. 7131774 and 77010174 planes are known which have a simpler design of their adjustment devices. These planes are provided with rotary handles having a substantially mushroom-like shape to act as an adjustment handle which acts via threaded spindles and nuts on the adjustable shoe formed with the second guiding plate. Between the shoe and the housing there are arranged springs which press the two parts apart. In rotating the adjustment handle for the largest depth of cut, the biasing springs become compressed. The latter adjustment devices are simpler in structure than those according to the abovementioned U.S. Pat. No. 3,407,857. Their disadvantage, however, is the feature that the adjustment handle serves simultaneously as a handle for guiding the plane itself, and consequently an unintentional change of the depth of cut of the plane can hardly be avoided during operation. The plane according to the German Gebrauchsmuster No. 7131774 is also provided with a circular setting index dial arranged on the housing concentrically to the rotary handle, the latter being provided with a pointer for adjusting the desired depth of cut. The disadvantage of this arrangement of the setting dial is the inconvenience to read respective settings of the depth of cut from different zones relative to the housing. This inconvenience also impedes fast setting of the depth of cut. In addition, the readings on dials in the planes according to the aforementioned Gebrauchsmuster do not correspond to the actual settings as soon as the adjustment handles are turned around from their zero position by more than one rotation.